This invention is directed to a lost motion clutch assembly which is a type of a positive clutch. A typical lost motion clutch has two parts, the first part being permitted to have a certain angular motion before it engages a portion of the second clutch part to cause it to start rotating. A difficulty with this type of lost motion clutch is that it has only a very limited angular amount of lost motion, e.g., about 90 degrees is a typical lost motion amount. Where a load is to be accelerated from rest, and the load has a high starting torque requirement, this is often extremely difficult to accomplish with a single-phase electric motor, which usually has a lower starting torque than running torque. Many electric motors have a third harmonic dip in the speed-torque curve and are suitable only for driving loads with low starting torque requirements. Even capacitor induction motors, whether of the capacitor-start or capacitor-run type, have a starting torque which is lower than the running or pull-out torque.
The problem to be solved, therefore, is how to construct a lost motion clutch with a sufficiently large angular amount of lost motion so that the motor driving the load through the lost motion clutch can accelerate to a point of near maximum torque to be able to start a load requiring high starting torque.
This problem is solved by a lost motion clutch assembly comprising, in combination, first, second, and third clutch members, means mounting said first and third clutch members coaxially on a shaft axis for limited relative rotation therebetween, means mounting said second clutch member between said first and third clutch members for movement in a plane normal to said axis, each said clutch member having at least a first engagement shoulder and said second member also having a second engagement shoulder, all said engagement shoulders being disposed at substantially equal radii, said first engagement shoulders of said first and second clutch members being disposed in a common plane of rotation and said second engagement shoulder of said second clutch members being disposed in the plane of rotation of said first engagement shoulder of said third clutch member, whereby upon initial rotation of said first clutch member in a first direction said lost motion clutch assembly has a predetermined angular lost motion before the third clutch member is rotated by engagement of said first and second engagement shoulders of said second clutch member with said first shoulders on said first and third clutch members.
Accordingly, an object of the invention is to provide a lost motion clutch assembly with an arcuate lost motion exceeding 90 degrees.
Another object of the invention is to provide a lost motion clutch assembly which includes three parts, with a lost motion between the first and second parts and another lost motion between the second and third parts.
A further object of the invention is to provide a lost motion cluch assembly which also functions as a thrust bearing during the lost motion action.
Still another object of the invention is to provide a lost motion clutch assembly which incorporates planetary action of balls during the angular lost motion.
Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing.